Processing cork and stoppers undergoes a continuous and careful visual quality selection. However, this is essentially based on the appreciation of the surface through visual inspection or photographic means, the presence of possible internal structural defects being yet to clarify. This fact renders it impossible to fully eliminate those stoppers that will not comply with their sealing function (for liquids and gases).
On the other hand, although preventive and curative processes have been developed by the cork industry to minimize the transference of compounds with an impact on taste, namely residues of chloroanisoles, there has been no technical or scientific activity towards improving or classifying the performance in respect of gas transference behaviour, e.g. oxygen.
Science literature frequently refers to the differences among cork stoppers and to their comparison with alternative systems (Crochiere, 2007; Kwiatkowski, 2007; Tran, 2007; Waters, 2007), but no attention has been drawn to optional segregation or manipulation practices regarding the gas transference behaviour, particularly in the case of cork stoppers.
The available results on the most recent research applied to the sealing of wine bottles do essentially outline the following aspects:
1st. Development of methods to measure oxygen permeability
2nd. Comparative study of different systems for sealing wine bottles
3rd. Sealing systems contribution to manage oxygen in the cellar, namely as a predicting tool for the wine's shelf-life in the market.
However, the applicants have no knowledge of any practical application of the performed researches in respect of improving the performance of cork stoppers.
On the other hand, at the level of methods developed to measure permeability, we have no knowledge of any non-destructive and non-invasive applications, which, primarily, may prove to result in a tool for the segregation of stoppers, based on their permeability, before they are really used.
In what concerns the interpretation of the gas diffusion and permeation phenomena, considering the characteristics of cork, the application of the principles of the conventional dynamics of fluids, wherein parameters such as density, pressure, temperature and flow of the particles are well defined in a determined point, is not feasible.
Considering its porous structure, the oxygen transportation regime is fundamentally conditioned by the average free trajectory1 of the means, the use of statistic mechanics being advisable.
It is within this scope that the novelty and pertinence of the present invention fits:
1. Constitute a data base that may allow the classification of the cork stopper in function of its structural and functional characteristics
2. Allow the identification of stoppers that shall not provide an effective sealing, namely the occurrence of structural defects;
3. Allow the classification of stoppers with different oxygen permeability;
4. Develop a classification methodology permitting their separation in order to place in the market lots with functional predictability.